A critical part of adapting to the higher temperatures that climate change brings will be the deployment of existing technologies to new sectors and regions. This paper examines the evolution of the temperature-mortality relationship over the course of the entire 20 th century in the United States both for its own interest but also to identify potentially useful adaptations that may be useful in the coming decades. There are three primary findings. First, the mortality impact of days with a mean temperature exceeding 80° F has declined by about 70%. Almost the entire decline occurred after 1960. There are about 14,000 fewer fatalities annually than if the pre-1960 impacts of high temperature on mortality still prevailed. Second, the diffusion of residential air conditioning can explain essentially the entire decline in hot day related fatalities. Third, using Dubin-McFadden's discrete-continuous model, we estimate that the present value of US consumer surplus from the introduction of residential air conditioning (AC) in 1960 ranges from $83 to $186 billion ($2012) with a 5% discount rate. The monetized value of the mortality reductions on high temperature days due to AC accounts for a substantial fraction of these welfare gains.

Between 1990 and 2008, air pollution emissions from US manufacturing fell by 60 percent despite a substantial increase in manufacturing output. We show that these emissions reductions are primarily driven by within-product changes in emissions intensity rather than changes in output or in the composition of products produced. We then develop and estimate a quantitative model linking trade with the environment to better understand the economic forces driving these changes. Our estimates suggest that the implicit pollution tax that manufacturers face doubled between 1990 and 2008. These changes in environmental regulation, rather than changes in productivity and trade, account for most of the emissions reductions. (JEL F18, H23, L60, Q52, Q53, Q56, Q58)

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The significance of grazing and enrichment to the Pleasant Pond phytoplankton community was examined through a series of enclosure cxpcriments.The addition of planktivororls fish led to the removal of large herbivores and to an order-of-magnitude increase in total phytoplankton biomass. This was a result of the appearance of several new algal species as well as the increase of most initial rcsidcnt species. Aphanizomenon flos-aquae was an exception to this pattern. This filamentous blue-green attains its maximum density in the presence of large Daphnia by forming large, ungrazeable colonies; Daphnia may provide a service to Aphanixomenon by removing most potential algal competitors. The addition of phosphorus and nitrogen had no quantitative effect on total phytoplankton biomass cithcr in the presence or absence of fish; changes in species composition did occur, several algae disappearing with enrichment.WC summarize the varied rcsponscs of lakes to enrichment and suggest that the community-level effects of enrichment can only be understood in the context of a framework that considers initial nutrient status and the strrrcturc of planktivorous fish populations.

a b s t r a c tThe paper estimates the effect of delayed school enrollment on student outcomes, using administrative data on Chilean students that include exact birth dates. Regression-discontinuity estimates, based on enrollment cutoffs, show that a one-year delay decreases the probability of repeating first grade by two percentage points, and increases fourth and eighth grade test scores by more than 0.3 standard deviations, with larger effects for boys. The paper concludes with implications for enrollment age policy.